You can also use the Photo Merge feature to create DNG panoramas from raw as well as non-raw files. The resulting files are 16-bit integer DNGs. Like the HDR DNGs, these are demosaiced DNGs saved as raw linear RGB data (see Figure 4.37). Although the images are partially processed, you still retain the ability to apply Develop module edits and update to later process versions as they become available.
One of the things I had noticed with the conventional Photoshop Photomerge workflow is how the Photomerge processing would often cause the highlight values to clip. You could carefully set the highlight end points at the pre-Photomerge stage, only to find them clipped in the resulting Photomerge composite. Therefore, being able to preserve the raw data when using the Photo Merge feature in Lightroom allows you to avoid this problem completely, maintain full control over the tones, and avoid undesired clipping. Since you have the ability to use Photo Merge to create HDR DNGs, you can also produce panoramas made up of HDR DNG files. However, the file size can end up being really huge if you adopt this approach, and it may take a long time to carry out all the processing. For optimum alignment, it is best to carry out the HDR Photo Merge first and then apply the panorama Photo Merge after.
To create a regular Photo Merge panorama, you first need to select a series of photographs that, when stitched together, will make up a panoramic view. When photographing such a sequence, it helps to have a decent overlap between each capture. There should be at least 25% overlap, or more if shooting with a wide-angle lens. It helps if you have the camera mounted on a tripod when you capture these; better yet, use a special tripod head that allows you to align the nodal point of the lens to the rotation axis. But you can also get good results shooting handheld. Ideally, the exposure setting should be consistent, but even if the photos are captured with a variance of exposure, the Photo Merge process can even these out to a certain extent. Lens warp, vignette, and chromatic aberration are applied to the images behind the scenes before stitching, so such settings in the source images will not be copied over to the resulting panorama DNG. Also not included are localized corrections, Upright and Crop adjustments. However, other adjustments are included, such as Basic panel and Tone Curve panel and color adjustments. In the case of the Lens Corrections panel, only defringe adjustments are copied. As before, to open Photo Merge in “headless” mode, hold down the Shift key as you select via the menu. In this mode, Lightroom processes the photos automatically without showing a dialog. Otherwise, you will see the dialog shown in Step 2, where you have the option to control the settings.
Figure 4.37 This shows the Metadata panel in DNG mode where a Photo Merge Panorama DNG file was selected. Although it does not indicate this is a panorama image, the clues here are the fact that there is no Mosaic Data and it has transparency data.
Panorama projection options
The Projection options are available in the Photo Merge – Panorama dialog (see Figure 4.38). In most cases, the Auto option will give you the best results, but not always, so it is good to be aware of the other options you can select to use as alternatives. The Perspective mode can produce good results when processing images that have been shot using a moderate wide-angle lens or longer. With wider-angle lens captures, it can produce distorted-looking results. The Cylindrical mode ensures that the photos are correctly aligned to the horizontal axis. This mode is particularly appropriate when merging photographs that make up a super-wide panorama. It will ensure the horizon line is kept as straight as possible. The Spherical mode transforms the photos both horizontally and vertically. This mode is more adaptable when it comes to aligning tricky panoramic sequences. So, for example, where you shoot a sequence of images that consists of two or more rows (such as in the following example), the Spherical projection mode may produce better results than the Cylindrical method.
Figure 4.38 The Projection options in the Photo Merge – Panorama dialog.
- To demonstrate the Photo Merge Panorama function, I selected the 16 photographs that are shown here in the Library module Survey view mode. I then went to the Photo menu and selected Photo Merge ➯ Panorama.
- This opened the Photo Merge Panorama dialog, where I could select the desired projection and preview the results before committing to creating a full Photo Merge. You can do as I did here and check the Auto Select Projection box to auto-select the most appropriate projection, in this case “Spherical.”
- After I clicked the Merge button in Step 2, Lightroom created a full Photo Merge Panorama DNG, renamed based on the most selected image in the photo selection, with a –Pano suffix added so as to distinguish it from the source images. The Develop settings applied here were based on whatever was the most selected photo in Step 1. Although, as I explained earlier, not all settings can be copied and applied.
- I then proceeded to apply a crop overlay to the panorama. Note that there is also an Auto Crop option (see dialog in Step 2), which when checked, applies a crop automatically. You still have the freedom to revise this if you wish.
- Finally, I went to the Basic panel in the Develop module and adjusted the settings to produce the optimized version shown here.